Internal combustion engines generally combust a mixture of fuel (e.g., gasoline, diesel, natural gas, etc.) and air. Prior to entering the engine, the air is typically passed through an air filtration system. A mass air flow (MAF) sensor is placed downstream of the air filter (i.e., on the clean side of the air filter media) and provides feedback to an engine control module (ECM). However, the air flow exiting the filter element may be inconsistent resulting in high variation of the MAF sensor to the ECM. Additionally, the orifice of the air filtration system that feeds the MAF sensor may cause a high pressure loss across the MAF sensor, thereby further reducing the accuracy of the MAF sensor output provided to the ECM.
U.S. Pat. No. 7,905,153, which is incorporated herein by reference in entirety, discloses a flow vortex suppression apparatus for use in an air intake duct having a MAF sensor. The flow vortex suppression apparatus includes an air flow permeable fibrous vortex dispersive media installed into the air duct in a position upstream of the MAF sensor and configured to occlude the air duct such that air flow in the duct is constrained to pass through the vortex dispersive media. The vortex dispersive media is configured and adapted to diffuse vortices and reduce air turbulence of an air stream entering the MAF sensor, thereby reducing variations and noise in a flow measurement signal from the mass air flow sensor.
U.S. Pat. No. 7,600,436, which is incorporated herein by reference in entirety, discloses a measuring system that is inserted into the course of a process line and serves for registering at least one measured variable of a medium flowing in the process line. The measuring system includes for such purpose a measuring transducer having a measuring tube serving for conveying medium being measured and a sensor arrangement, which has at least one sensor element reacting primarily to the measured variable to be registered, and which delivers by means of at least one sensor element at least one measurement signal influenced by the measured variable.
U.S. Pat. No. 7,497,301, which is incorporated herein by reference in entirety, discloses an acoustic silencer provided by a tubular member extending along an axis and having a hollow interior defining an axial flow path therethrough. The tubular member has a sidewall with an interior face facing the hollow interior and having quarter wave resonators formed by blind holes therein.
U.S. Pat. No. 7,377,954, which is incorporated herein by reference in entirety, discloses an air filtration cartridge with annular filter media having a hollow interior and extending axially between first and second distally opposite end caps. The first end cap is an outlet end cap having flow straightening structure integrally formed therewith and spanning the hollow interior. The second end cap is a closed end cap having an interior face having quarter wave resonators formed by blind holes therein.
U.S. Pat. No. 6,655,207, which is incorporated herein by reference in entirety, discloses an integrated module for measuring a flow rate of a fluid, whether gaseous or liquid, with a flow restrictor comprising a plurality of orifices adapted to a flow channel of the integrated module and a sensor mounted to measure a property of the fluid at said flow restrictor corresponding to the flow rate. The integrated module provided may be used in numerous flow systems, such as reactors, ventilators and respirators, and has the benefit of better laminarization of the flow as well as better calibration between the flow sensor and the flow restrictor for more accurate flow measurements.
U.S. Pat. No. 6,267,006, which is incorporated herein by reference in entirety, discloses an air induction assembly disposed in an intake passage through which air flows to an engine. The air induction assembly has a conduit member which defines an air flow path. A MAF sensor is located in the intermediate conduit portion and is in fluid communication with the air flow path. The MAF sensor is operative to generate an output signal corresponding to air flow rate within the intermediate conduit portion. A plurality of flow conditioning elements (FCEs) in the airflow path produces a uniform airflow with low turbulent fluctuations to the MAF sensor under all vehicle and engine speeds without excessively restricting the air flowing to the engine.
U.S. Pat. No. 6,199,434, which is incorporated herein by reference in entirety, discloses a device for metering the volume of gas flowing in a pipe, downstream from an expander-regulator, comprising in succession a flow straightener, a velocity-measuring flowmeter, and a silent flowrate limiter. The straightener comprises a support ring in which there are mounted a first perforated plate having holes distributed over its surface, together with a first porous plate and a spacer in the form of an annulus co-operating with the first perforated plate. The limiter comprises an upstream web defining a second perforated plate perforated by a defined number of calibrated holes, the total flow section thereof being much less than the total flow section of the first perforated plate, a second perforated plate, and a downstream web defining a third perforated plate having holes of total flow section that is much greater than the total flow section of the second perforated plate of the upstream web.
U.S. Patent Application Publication No. 2005/0087012 discloses a mass tube for a MAF sensor comprising a metal grid acting as a flow rectifier arranged perpendicular to the air flow. At least two fixing elements are arranged on the measuring tube, said elements extending inwards in a radial manner, whereon the metal grid is fixed by pre-tensioning.